/**
 *create by 2012-08-25 pm 17:48
 *@author hexinglun@gmail.com
 *BASE64 Encode and Decode By UTF-8 unicode
 *可以和java的BASE64编码和解码互相转化
 */
(function () {
    var BASE64_MAPPING = [
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
        'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
        'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
        'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
        'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
        'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
        'w', 'x', 'y', 'z', '0', '1', '2', '3',
        '4', '5', '6', '7', '8', '9', '+', '/'
    ];

    /**
     *ascii convert to binary
     */
    var _toBinary = function (ascii) {
        var binary = new Array();
        while (ascii > 0) {
            var b = ascii % 2;
            ascii = Math.floor(ascii / 2);
            binary.push(b);
        }
        /*
        var len = binary.length;
        if(6-len > 0){
            for(var i = 6-len ; i > 0 ; --i){
                binary.push(0);
            }
        }*/
        binary.reverse();
        return binary;
    };

    /**
     *binary convert to decimal
     */
    var _toDecimal = function (binary) {
        var dec = 0;
        var p = 0;
        for (var i = binary.length - 1; i >= 0; --i) {
            var b = binary[i];
            if (b == 1) {
                dec += Math.pow(2, p);
            }
            ++p;
        }
        return dec;
    };

    /**
     *unicode convert to utf-8
     */
    var _toUTF8Binary = function (c, binaryArray) {
        var mustLen = (8 - (c + 1)) + ((c - 1) * 6);
        var fatLen = binaryArray.length;
        var diff = mustLen - fatLen;
        while (--diff >= 0) {
            binaryArray.unshift(0);
        }
        var binary = [];
        var _c = c;
        while (--_c >= 0) {
            binary.push(1);
        }
        binary.push(0);
        var i = 0, len = 8 - (c + 1);
        for (; i < len; ++i) {
            binary.push(binaryArray[i]);
        }

        for (var j = 0; j < c - 1; ++j) {
            binary.push(1);
            binary.push(0);
            var sum = 6;
            while (--sum >= 0) {
                binary.push(binaryArray[i++]);
            }
        }
        return binary;
    };

    var __BASE64 = {
        /**
         *BASE64 Encode
         */
        encoder: function (str) {
            var base64_Index = [];
            var binaryArray = [];
            for (var i = 0, len = str.length; i < len; ++i) {
                var unicode = str.charCodeAt(i);
                var _tmpBinary = _toBinary(unicode);
                if (unicode < 0x80) {
                    var _tmpdiff = 8 - _tmpBinary.length;
                    while (--_tmpdiff >= 0) {
                        _tmpBinary.unshift(0);
                    }
                    binaryArray = binaryArray.concat(_tmpBinary);
                } else if (unicode >= 0x80 && unicode <= 0x7FF) {
                    binaryArray = binaryArray.concat(_toUTF8Binary(2, _tmpBinary));
                } else if (unicode >= 0x800 && unicode <= 0xFFFF) {//UTF-8 3byte
                    binaryArray = binaryArray.concat(_toUTF8Binary(3, _tmpBinary));
                } else if (unicode >= 0x10000 && unicode <= 0x1FFFFF) {//UTF-8 4byte
                    binaryArray = binaryArray.concat(_toUTF8Binary(4, _tmpBinary));
                } else if (unicode >= 0x200000 && unicode <= 0x3FFFFFF) {//UTF-8 5byte
                    binaryArray = binaryArray.concat(_toUTF8Binary(5, _tmpBinary));
                } else if (unicode >= 4000000 && unicode <= 0x7FFFFFFF) {//UTF-8 6byte
                    binaryArray = binaryArray.concat(_toUTF8Binary(6, _tmpBinary));
                }
            }

            var extra_Zero_Count = 0;
            for (var i = 0, len = binaryArray.length; i < len; i += 6) {
                var diff = (i + 6) - len;
                if (diff == 2) {
                    extra_Zero_Count = 2;
                } else if (diff == 4) {
                    extra_Zero_Count = 4;
                }
                //if(extra_Zero_Count > 0){
                //	len += extra_Zero_Count+1;
                //}
                var _tmpExtra_Zero_Count = extra_Zero_Count;
                while (--_tmpExtra_Zero_Count >= 0) {
                    binaryArray.push(0);
                }
                base64_Index.push(_toDecimal(binaryArray.slice(i, i + 6)));
            }

            var base64 = '';
            for (var i = 0, len = base64_Index.length; i < len; ++i) {
                base64 += BASE64_MAPPING[base64_Index[i]];
            }

            for (var i = 0, len = extra_Zero_Count / 2; i < len; ++i) {
                base64 += '=';
            }
            return base64;
        },
        /**
         *BASE64  Decode for UTF-8
         */
        decoder: function (_base64Str) {
            var _len = _base64Str.length;
            var extra_Zero_Count = 0;
            /**
             *计算在进行BASE64编码的时候，补了几个0
             */
            if (_base64Str.charAt(_len - 1) == '=') {
                //alert(_base64Str.charAt(_len-1));
                //alert(_base64Str.charAt(_len-2));
                if (_base64Str.charAt(_len - 2) == '=') {//两个等号说明补了4个0
                    extra_Zero_Count = 4;
                    _base64Str = _base64Str.substring(0, _len - 2);
                } else {//一个等号说明补了2个0
                    extra_Zero_Count = 2;
                    _base64Str = _base64Str.substring(0, _len - 1);
                }
            }

            var binaryArray = [];
            for (var i = 0, len = _base64Str.length; i < len; ++i) {
                var c = _base64Str.charAt(i);
                for (var j = 0, size = BASE64_MAPPING.length; j < size; ++j) {
                    if (c == BASE64_MAPPING[j]) {
                        var _tmp = _toBinary(j);
                        /*不足6位的补0*/
                        var _tmpLen = _tmp.length;
                        if (6 - _tmpLen > 0) {
                            for (var k = 6 - _tmpLen; k > 0; --k) {
                                _tmp.unshift(0);
                            }
                        }
                        binaryArray = binaryArray.concat(_tmp);
                        break;
                    }
                }
            }

            if (extra_Zero_Count > 0) {
                binaryArray = binaryArray.slice(0, binaryArray.length - extra_Zero_Count);
            }

            var unicode = [];
            var unicodeBinary = [];
            for (var i = 0, len = binaryArray.length; i < len;) {
                if (binaryArray[i] == 0) {
                    unicode = unicode.concat(_toDecimal(binaryArray.slice(i, i + 8)));
                    i += 8;
                } else {
                    var sum = 0;
                    while (i < len) {
                        if (binaryArray[i] == 1) {
                            ++sum;
                        } else {
                            break;
                        }
                        ++i;
                    }
                    unicodeBinary = unicodeBinary.concat(binaryArray.slice(i + 1, i + 8 - sum));
                    i += 8 - sum;
                    while (sum > 1) {
                        unicodeBinary = unicodeBinary.concat(binaryArray.slice(i + 2, i + 8));
                        i += 8;
                        --sum;
                    }
                    unicode = unicode.concat(_toDecimal(unicodeBinary));
                    unicodeBinary = [];
                }
            }
            return unicode;
        }
    };

    window.BASE64 = __BASE64;
})();